Site and Environmental Analysis
Site and environmental analysis asks what the land will allow before you design what the client wants. The exam tests zoning-envelope arithmetic, solar and wind reasoning, drainage and soils judgment, and environmental due diligence.
Core rules
- Zoning envelope first. Floor area ratio (FAR) = total gross floor area ÷ lot area. Coverage limits the footprint; setbacks and height limits shape the buildable volume. The binding constraint is whichever produces the smallest building.
- Solar geometry. Sun path varies with latitude: a low winter altitude angle drives deep penetration and glare; a high summer angle makes overhangs effective on south facades. East and west exposures are the hardest to shade. Plot altitude and azimuth for the design days before you commit to orientation or fin depth.
- Water. Pre-development versus post-development runoff, grading to keep flow away from foundations, and low-impact strategies (biofiltration, permeable paving, cisterns) that reduce discharge. Respect floodplain and freeboard requirements.
- Soils and due diligence. Typical allowable bearing values - granular soils 3,000–6,000 psf, stiff clay 2,000–4,000 psf, soft or organic soils well under 1,000 psf - are planning figures only; a geotechnical report governs. A Phase I environmental site assessment (ASTM E1527) precedes acquisition.
- Context. Access and sight distance, noise contours, prevailing winds, air quality, views, easements, and utility locations all belong in the site analysis narrative.
Worked example
Lot of 24,000 SF, FAR 2.5, 50% coverage, 85 ft height limit, 13 ft floor-to-floor. FAR permits 60,000 GSF; coverage permits a 12,000 SF footprint; height permits 85 ÷ 13 = 6 floors (78 ft). The most restrictive combination is 12,000 × 6 = 72,000 GSF potential, but FAR caps it at 60,000 GSF - five floors at 12,000 SF, leaving one floor of unused height and coverage capacity.
Traps
- Computing FAR from net rather than gross area, or including parking garages when the code exempts them.
- Assuming a due-south facade is always best; unshaded east and west glass often drives cooling load.
- Using textbook bearing capacity in place of the geotechnical report.
- Ignoring off-site drainage and downstream flooding obligations.